Specifies how far behind schedule a component is for processing samples.
(const REFERENCE_TIME*) How far behind the component is, in 100-nanosecond units. If this value is positive, the component is behind schedule. If this value is negative, the component is ahead of schedule.
A custom presenter for the Enhanced Video Renderer (EVR) filter can send this message to the EVR, to notify the EVR whether the presenter is behind schedule or ahead of schedule.
The simplest way to calculate lParam1 is: QPC now QPC target, where QPC now is the clock time now, and QPC target is the presentation time.